Field of the Invention
The present invention relates to a medical instrument, in particular a surgical instrument, with an elongate shank, and a tool which is arranged on a distal end portion of the shank and which comprises two tool elements interacting with each other, in particular for the purpose of holding an object, of which at least one tool element is movable by means of a longitudinally displaceable first transmission element.
Description of the Background Art
In medical instruments of this kind, it is often necessary that an object should be grasped and held firmly with the tool in order to be able to move the object by means of the surgical instrument and, for example, perform surgical manipulations using the object. For example, a surgical needle should be grasped and held as firmly as possible in order to insert the needle into tissue. For this purpose, it is desirable for the interacting tool elements to be blocked or locked in a holding position in which the surgical element is grasped, such that a user does not have to apply any more force in order to continue holding the object and is able to move the latter comfortably. Locking of this kind can be obtained, for example, by means of a catch which is arranged on a handle and with which a grip, with which the at least one movable tool element can be actuated via a pull rod, can be locked in a holding position. In this way, the object can be held securely and firmly without the user having to continue applying force for this purpose. However, the pull rod is in this case tensioned, which is disadvantageous in terms of the handling and durability of the instrument. Moreover, in the case where the tool is mounted rotatably about a longitudinal axis, the rotary bearing of the tool is tensioned in the locked state and can be rotated only by application of considerable force. The high degree of loading during rotation can also cause damage to the instrument.
DE 10 2009 055 747 A1 discloses surgical forceps in which a relative movement of the jaw parts of the forceps mouth is controlled via the engagement of at least one cam on the forceps mouth or on an actuating rod, in a groove arranged on the actuating rod or on the forceps mouth, the groove being inclined with respect to the direction of displacement of the actuating rod. The groove is provided, in at least some regions, with an angle of inclination which is smaller than the angle of inclination up to which self-retention in the groove occurs. The self-retention ensures that, after an object has been clamped in the forceps mouth by actuation of the actuating rod, the clamped position is maintained, even if the actuating rod is let go.
EP 2 522 280 A1 discloses a medical instrument, in particular a surgical needle holder, comprising two jaw parts, wherein at least one of the jaw parts is pivotable relative to the other one between a grasping state for grasping the object and a release state for releasing the object. The instrument has a latching mechanism for blocking the at least one pivotable jaw part in the grasping state, wherein a connection pin, connecting the pivotable jaw part to a latching element, is received in an elongate opening of the latching element. The elongate opening is divided into several segments by periodical projections, such that the pivotable jaw part is pivotable stepwise from one stable and locked position to another stable and locked position.
According to U.S. Pat. No. 7,896,900 B2, a medical instrument, in particular a surgical needle holder, is provided with a latching mechanism for immobilizing at least one pivotable jaw part in a grasping state for the purpose of grasping an object, wherein the latching mechanism comprises a latching element formed by an elastically deformable and, for example, C-shaped lever. By axial movement of a force transmission element, the lever is caused to snap-fit into a locked and stable state.
In the abovementioned solutions, the jaw parts are locked or immobilized in a holding position, the latching mechanism being arranged in the distal area of the instrument. However, it has been found that a sufficient holding force, in particular for holding a surgical needle, cannot always be achieved in this way, and/or that a relatively high force has to be applied for locking and unlocking.